Slow Car Fast
July 13, 2011 - I found something else while I was under the car: my vibration.
It wasn't the exhaust as I've always thought. I discovered that the block is actually hitting the driver's side footwell. Not very much of it, but you don't need much. That's where the deep vibration under power comes from. Unfortunately, it's in a spot that's pretty much inaccessible.
There's no way you can reach it from the engine bay. From inside the car, I just can't figure out how to cut the panel to give myself the needed 1/8" of clearance. The interference is right beside the throttle pedal, where there's a nice deep insert for the steering column. I just can't get in there.
Using a prybar to open up the clearance a bit isn't an option either. The multiple folds of the sheetmetal and a nice 90 degree seam mean that this is one very solid piece of car. Besides, even if I did manage to move the sheetmetal I'd probably have trouble getting the throttle pedal clear.
Two options present themselves. One, pull the engine and grind down the offending protrusion on the block. Ugh. Two, see if there's any slop in my motor mounts that will let me rock the engine over slightly. Or maybe I could shim it. Come to think of it, this could be because of my change to rubber motor mounts. I'll see what I can do there.
entry 629 - tags: motor mounts, interference
July 18, 2011 - I spent most of the weekend on other things, but I did crawl under the MG to take a shot at solving the vibration.
One of my thoughts was that I might be able to slot the motor mount holes to move the engine slightly. So I was quite happy to see that they were already slotted, and that I had lots of room to move the engine in the direction I wanted to move it.
After some wrenching, levering and jacking, I had the engine tightened back up in my new location. The gap between the body and the offending bump on the block was a bit larger. A test drive showed that the vibration was dramatically decreased. I'm not even sure if it's still hitting - there's still a bit of a rumble under certain conditions, but it seems to be more restricted to certain RPM ranges which tells me I'm dealing with an acoustic resonance. So, good progress then!
entry 631 - tags: motor mounts, interference